Part of Michael's problem was that his idea of "legitimacy" was doing business in the "legitimate" world and backing it up with his position in the mob. In effect he was stuck in the passt. By the time he reached his exalted position in The Commission, the mob was losing power, and being a mob boss wasn't all that it was back in the day. The times and his own family left Michael behind in the dirt, and he never got that.